Method for Manufacturing Coated Film

The present invention relates to a method for manufacturing a coated film and an apparatus for manufacturing a coated film, and particularly relates to a method and an apparatus for manufacturing a coated film used in a separator of a battery or the like.

In recent years, batteries such as lithium ion batteries have been actively used for automobiles and infrastructure. In a battery such as a lithium ion battery, a positive electrode material and a negative electrode material are separated by a porous film called a separator. The separator has, for example, a plurality of micropores through which lithium ions can pass, and charging and discharging can be repeated by the lithium ions moving between the positive electrode material and the negative electrode material through the pores. As described above, the separator has a role of separating the positive electrode material and the negative electrode material to prevent a short circuit.

In addition, when the temperature inside the battery becomes high for some reason, the micropores of the separator are closed to stop the movement of lithium ions, thereby stopping the battery function (shutdown function).

As described above, the separator plays a role of a battery safety device, and it is important to improve the mechanical strength and heat resistance of the separator.

For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2016-183209) discloses a technique of forming a coating layer containing inorganic particles and a binder resin composition on at least one surface of a polyolefin resin porous film.

Further, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2017-068900) discloses a technique of forming a coating layer by applying a coating liquid containing a filler and a resin binder on a polyolefin-based resin porous film and then drying the liquid.

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-183209 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-068900

The inventors of the present invention have conducted research and development on a coating technique for forming a coating layer on a surface of a base material in order to improve the mechanical strength and heat resistance of the base material (porous film) of the separator of the battery.

In the process of the research and development, wrinkles and drying defects occurred on the base material in the coating and drying processing of the coating liquid, and a favorable coating technique was found as a result of diligent studies on the elimination of these problems.

Other problems and novel features will be apparent from the description of this specification and accompanying drawings.

A method for manufacturing a coated film disclosed in this application includes: (a) a step of applying a coating liquid to a first surface of a base material taken out from an unloading unit; (b) a step of forming a coating layer on the first surface of the base material by drying the coating liquid on the base material; and (c) a step of taking in the base material on which the coating layer has been formed in a loading unit. The base material is continuously arranged from the unloading unit to the loading unit, tension cut of the base material is performed by a first suction roll after the base material is taken out from the unloading unit and before the step (b), and tension cut of the base material on which the coating layer has been formed is performed by a second suction roll before the step (c).

An apparatus for manufacturing a coated film disclosed in this application includes: an unloading unit from which a base material is taken out; a coating unit configured to apply a coating liquid to a first surface of the base material; a drying unit configured to form a coating layer on the first surface of the base material by drying the coating liquid on the base material; and a loading unit configured to load the base material on which the coating layer has been formed. A first suction roll is arranged between the unloading unit and the drying unit, and a second suction roll is arranged between the drying unit and the loading unit.

According to the method for manufacturing a coated film disclosed in this application, it is possible to manufacture a coated film having good characteristics.

According to the apparatus for manufacturing a coated film disclosed in this application, it is possible to manufacture a coated film having good characteristics.

Hereinafter, embodiments will be described in detail with reference to examples and drawings. Note that members having the same function are denoted by the same reference characters throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

1 FIG. 2 FIG. is a diagram schematically showing a configuration of an apparatus for manufacturing a coated film according to the present embodiment. Also,is a cross-sectional view showing a process for forming the coated film according to the present embodiment.

2 FIG. First, the process for forming the coated film will be described with reference to.

2 FIG.(A) 1 1 1 1 1 a As shown in, a base materialmade of a porous film is prepared. The porous film used as the base materialis made of, for example, a polyolefin-based resin. The thickness of the base materialis, for example, about 5 μm to 50 μm, and the width is, for example, about 200 mm to 3000 mm. The pore size distribution of microporesis, for example, about 10 nm to 10 μm, and the average pore size is, for example, about 100 nm to 900 nm. The Gurley value of the base materialis, for example, about 100 to 300 sec/100 cc.

2 FIG.(B) 1 1 10 1 1 1 Next, as shown in, the surface (first surface) of the base materialis subjected to surface processing. For example, the surface of the base materialis irradiated with the corona discharge by using a corona discharge irradiation device. As a result, the surface of the base materialis modified. Specifically, the wettability of the coating liquid is enhanced on the surface of the base material. Note that such a surface processing is not indispensable and may be omitted depending on the type of the base material.

2 FIG.(C) 1 3 a Next, as shown in, a coating liquid is applied to the surface of the base materialto form a coating film. The coating liquid contains a filler and a dispersion medium. As the filler, inorganic substances such as alumina, silica, aluminum hydroxide, and boehmite, cellulose, and the like can be used. As the dispersion medium, an aqueous solvent or an organic solvent can be used. Further, a binder may be added. As the binder, a side chain or cyclic polymer resin, an acrylic resin, a thermoplastic fluoropolymer, or the like can be used. As the coating device, for example, a gravure coating device can be used. Further, in addition to the filler and the binder, SBR (styrene/butadiene rubber) or a polymer having high ionic conductivity may be added before use.

2 FIG.(D) 3 1 3 5 1 3 1 1 3 3 3 1 1 3 1 3 a b b a b b b a b b Next, as shown in, the coating filmon the base materialis dried to form a coating layer. Through the above process, a separator (coated film)composed of the base material (porous film)and the coating layercan be formed. The base material (porous film)is provided with a large number of micropores, and the coating layeris provided on the surface thereof. The coating layercontains, for example, cellulose and alumina. For example, as shown in the enlarged view, the coating layeris not formed so as to cover all the microporesof the base material, and the coating layeritself has air permeability. For example, the Gurley value (air permeability, [sec/100 cc]) of the base material(separator) on which the coating layerhas been formed is 10 or more and 3000 or less, and the air permeability is ensured.

1 FIG. The case in which the formation of the coating layer mentioned above is performed by using the apparatus (system) shown inwill be described below.

1 FIG. 1 1 1 5 3 1 1 b As shown in, the apparatus for manufacturing the coated film includes an unwinding unit UW for unwinding the base materialand a winding unit WD for winding the base material. The base materialis continuously arranged from the unwinding unit UW to the winding unit WD, and the separator (coated film)is completed by forming the coating layeron the surface (first surface) of the base materialbetween the unwinding unit UW and the winding unit WD. According to this apparatus for manufacturing the coated film, the scroll-shaped (rolled strip-shaped) base materialcan be continuously processed, and the separator can be efficiently formed. In this specification, the side of the unwinding unit UW may be referred to as upstream, and the side of the winding unit WD may be referred to as downstream.

10 20 30 1 3 b Specifically, a surface processing unit (), a coating processing unit (), and a drying processing unit () are arranged between the unwinding unit UW and the winding unit WD. The base materialis processed in each processing unit while being guided by a plurality of rolls (guide rolls) R, and the coating layeris formed on the surface thereof. This will be described in detail below.

1 10 10 10 1 1 The base materialunwound from the unwinding unit UW is conveyed to the surface processing unit (). In this surface processing unit (), the corona discharge irradiation deviceis arranged, and the surface of the base materialis irradiated with corona discharge (corona processing). As a result, the surface of the base materialis modified, and the wettability of the coating liquid is enhanced in the coating processing described later.

1 20 1 10 20 The base materialsubjected to the surface processing (here, corona processing) is guided by the roll R and conveyed to the coating processing unit. Here, the base materialis inverted by the roll R, and the first surface subjected to the surface processing (upper side in the surface processing unit ()) becomes the lower side in the coating processing unit ().

20 20 20 1 3 a a. In the coating processing unit (), the gravure coating deviceis arranged, and the coating liquidis applied (coated) to the first surface of the base material. The coating film is indicated by

1 3 30 1 3 20 30 a a The base materialon which the coating filmhas been formed is guided by the roll R and conveyed to the drying processing unit (). Here, the base materialis inverted by the roll R, and the first surface on which the coating filmhas been formed (lower side in the coating processing unit ()) becomes the upper side in the drying processing unit ().

30 30 3 1 3 30 1 2 3 a b In the drying processing unit (), a drying oven (conveyor drying oven)is arranged, and the liquid component of the coating filmof the base materialconveyed by the roll R is vaporized to form the coating layer. For example, the drying ovenhas three drying chambers (covers)D,D, andD, and heated air is introduced from a nozzle (not shown) in each drying chamber. The temperature of the heated air is controlled by a heating unit (heater or the like) (not shown).

1 As described above, the strip-shaped base materialis processed in each processing unit while being guided by the plurality of rolls (guide rolls) R.

1 FIG. 30 1 1 1 20 1 30 1 1 1 1 Here, in the present embodiment, as shown in, suction rolls SR are provided before and after the drying processing unit (). The tension cut of the base materialis performed by the suction rolls SR. By the tension cut, it is possible to adjust the tension of the base materialto be different between the upstream and the downstream starting from the suction roll SR as a point of origin. For example, in an apparatus having a plurality of processing units, the state of the base material (film)changes depending on each processing. For example, in the coating processing unit (), the thickness of the base materialchanges. Further, in the drying processing unit (), the base materialexpands and contracts. If the base materialis controlled to have the same tension uniformly in the apparatus regardless of such a change in the state of the base material, there is a concern that the base materialmay flutter, sag, or tear.

30 30 30 30 30 Therefore, for example, the tension cut is performed before and after the drying processing unit (). As a result, the tension can be adjusted in three sections such as the section from the unwinding unit UW to the inlet of the drying processing unit (), the section from the inlet of the drying processing unit () to the outlet of the drying processing unit (), and the section from the outlet of the drying processing unit () to the winding unit WD.

1 1 Such tension cut can also be performed by using nip rolls described later. However, when the nip rolls that physically sandwich the base materialare used, they become a conveyance resistance even they are is of a driven type, and the winding tension increases. On the other hand, when the suction roll SR is used, the conveyance resistance of the base materialcan be reduced. Here, for example, if the suction rolls SR in the apparatus are removed, the winding tension increases.

1 1 1 1 1 1 1 1 1 As described above, the strip-shaped base materialis processed in each processing unit while being guided by the plurality of rolls (guide rolls) R. At this time, if the state of the base material (film)is changed by each processing, the base materialmay be sagged or torn. Therefore, by performing the tension cut of the base material, it is possible to suppress the base materialfrom being sagged and torn, and the base materialcan be processed without troubles. Further, it is not necessary to reduce the processing speed (line speed, conveyance speed) of the base materialin order to prevent the base materialfrom being sagged or torn, and the base materialcan be processed at high speed.

3 FIG. 3 FIG.(A) 3 FIG.(B) is a diagram showing the configuration of the suction roll SR.is a perspective view, andis a cross-sectional view.

3 FIG.(A) 3 FIG.(B) 1 1 1 1 As shown in, the suction roll SR has a shaft portion and a cylindrical portion. A plurality of holes P are provided in the side surface of the cylindrical portion. Then, the cylindrical portion is connected to a suction unit (decompression pump or the like), and a partial region inside the cylindrical portion comes into a suction state when the suction roll SR is in operation. This partial region is a region BA having a fan-shaped cross section in contact with the base material. Therefore, as shown in, the base materialis sucked to the side surface of the cylindrical portion and is conveyed by the rotation of the cylindrical portion. The suction pressure (pressure of the partial region BA inside the cylindrical portion) is preferably 3 MPa or less. If it exceeds 3 MPa, the base materialmay be dragged into the holes P of the suction roll SR. In particular, when a thin base material (10 μm or less) is used as the base material, the suction pressure is preferably 2.5 MPa or less, and more preferably 1.5 MP or less. The size, shape, and number of holes P provided in the suction roll SR can be changed as appropriate.

4 FIG. 4 FIG. 1 2 1 2 1 2 1 1 2 Nip rolls can be presented as an example of such a roll for tension cut (roll for tension control).is a perspective view showing the configuration of the nip rolls. As shown in, the nip rolls have a roll Rand a roll R, and for example, a pressure is applied to the roll Rtoward the roll R. In other words, the roll Ris pressed to the roll R. Tension cut can be performed by passing the base materialbetween the roll Rand the roll R.

1 1 2 1 2 1 1 2 1 2 1 5 FIG. 5 FIG.(A) According to the study by the inventors, it was found that wrinkles were likely to occur on the base materialwhen the nip rolls (R, R) were used as the rolls for tension cut.is a diagram schematically showing the state of the base material when the nip rolls are used. As shown in, at the moment of passing between the roll Rand the roll R, the base materialis thinned and flattened by the pressure (load, nip pressure) between the roll Rand the roll R. However, it is conceivable that, after passing between the roll Rand the roll R, the base materialis released from the pressure and returned to the original shape (thickness), and wrinkles are formed.

1 2 1 According to the inventors, although the conditions under which wrinkles did not occur were intensively studied by changing various conditions (pressure, winding tension, processing speed, etc.) by using the nip rolls (R, R), starting with comparative examples described later, it was found difficult to eliminate the occurrence of wrinkles. In particular, when the thickness of the base materialwas small, since the cross-sectional area was small and the applied pressure was relatively increased, the occurrence of wrinkles was noticeable.

1 2 1 On the other hand, in the present embodiment, the occurrence of wrinkles can be suppressed by using the suction roll instead of the nip rolls (R, R). In particular, even when the base materialis thinned, the occurrence of wrinkles can be effectively suppressed.

1 2 As described above, in the present embodiment, the tension cut works effectively, so that the winding tension can be suppressed as compared with the case of using the nip rolls (R, R).

1 1 2 1 1 1 2 1 When coating is performed at high speed in order to increase productivity, the tension of the base materialbetween the rolls increases in the apparatus in which the nip rolls (Rand R) are installed as described above. Further, since the base material (film)is compressed in the thickness direction, the elastically deformed base materialis restored to its original width after passing through the nip rolls (Rand R), so that wrinkles are likely to occur on the base material.

1 1 1 1 1 1 On the other hand, if the tension between the rolls R is lowered in order to improve the wrinkles of the base materialhaving a small film thickness, air enters between the roll R and the base material, so that the base materialfloats and meanders. Since the amount of air that causes the base materialto float increases in proportion to the conveyance speed of the base material, the base materialtends to float especially when the coating is performed at high speed.

1 1 2 However, when the suction roll SR is used, the tension cut functions effectively, so that the meandering caused by the excessive or insufficient tension between the rolls R and the occurrence of wrinkles caused by the physical contact as in the case of using the nip rolls are suppressed. Therefore, when the suction roll SR is used, the base materialcan be conveyed at a higher speed than when the nip rolls (Rand R) are used.

1 6 FIG. 7 FIG. Further, since the base materialcan be conveyed at high speed, it is not necessary to use a vertical-type coating device in the gravure coating device, and a horizontal-type coating device can be used.is a cross-sectional view showing a horizontal-type coating device. Also,is a cross-sectional view showing a vertical-type coating device.

20 20 20 20 20 20 20 20 6 FIG. 6 FIG. b a b c a c a The horizontal-type coating device () shown inincludes a chamber (tank)for storing the coating liquid, a coating roll CR, a part of which is immersed in the chamber (tank), and a bladefor preventing the scattering of the coating liquid. The bladeis arranged on the side of the rotation direction of the coating roll CR (left side in) so as to hold the coating liquidadhered to the surface of the coating roll CR.

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 7 FIG. b a c b b a a b c c a c c b a On the other hand, in the vertical-type coating device () shown in, the chamber (tank)is arranged in the vertical direction (direction parallel to the gravity direction). In this case, it is necessary to hold the coating liquidby two bladesarranged above and below the chamber (tank). Further, if the capacity of the chamber (tank)is made too large, the blade that holds the coating liquidbends, and the coating liquidcannot be held. Accordingly, in the vertical-type coating device (), the capacity of the chamber (tank)cannot be increased, and the wear of the bladeitself and the wear of the coating roll CR which is in contact with the bladevia the coating liquidare increased. As described above, the coating liquid contains a hard filler such as alumina. Therefore, the bladeand the coating roll CR which are in contact with each other via the coating liquid are scraped and worn. On the other hand, in the present embodiment, since the horizontal-type coating device () can be incorporated, the wear of the bladeand the coating roll CR can be reduced. Further, the capacity of the chamber (tank)can be increased, and the coating liquidis unlikely to run out even if high-speed processing is performed.

1 2 1 As described above, since the tension cut works effectively in the present embodiment, the winding tension can be suppressed as compared with the case of using the nip rolls (R, R). Therefore, high-speed processing is possible. Namely, each processing can be performed while conveying the base materialat high speed.

30 1 1 Here, in the drying processing unit (), the internal temperature of each cover (each drying chamber) is preferably uniform. However, with the high-speed conveyance of the base material, an accompanied flow comes in from the lower part of the cover (the gap between the side wall of the cover and the base material), and the temperature inside the cover may be lowered. Therefore, it is preferable to control the temperature in consideration of the accompanied flow.

8 FIG. 9 FIG. 1 FIG. 30 1 is a cross-sectional view showing the state of the drying chamber in the present embodiment.is a cross-sectional view showing the state of the drying chamber in the comparative example. Here, among the three drying chambers provided in the drying processing unit () shown in, the drying chamberD arranged at the most upstream side will be described.

8 FIG. 31 1 31 1 31 a a a. As shown in, a nozzleis provided inside the drying chamberD, and heated dry air (heating fluid) DA is discharged from the tip of the nozzle. In other words, the heated dry air DA is blown to the base materialfrom the tip of the nozzle

31 31 1 31 1 1 1 a a b For example, the nozzleis provided at the center of the drying chamber. The planar shape of the nozzlemay be spot-shaped (circular) or line-shaped (rectangular). Here, the internal temperature of the drying chamberD is measured by a thermocouple. A thermocouple is a temperature sensor that measures the temperature (temperature difference) based on the thermoelectromotive force at the junction between two or more types of metals. If the temperature inside the drying chamberD deviates from the set temperature as a result of measuring the temperature inside the drying chamberD by this thermocouple (temperature sensor), the temperature of the heated dry air DA is adjusted by a heater (not shown), and the temperature in the drying chamberD is maintained at the set temperature.

31 31 1 31 1 3 1 1 b a b a In the present embodiment, the thermocoupleis provided between the side wall of the drying chamber (cover) on the upstream side and the nozzle(regionA). By arranging the thermocouplein this way, the temperature drop in the drying chamberD due to the accompanied flow AF can be appropriately corrected, and the coating filmformed on the surface of the base materialcan be dried accurately. Here, the side wall of the drying chamber (cover) on the upstream side is the side wall that the base materialfirst crosses, and in other words, it is the side wall located on the upstream side, of the two side walls extending in the direction intersecting the conveyance direction.

9 FIG. 31 31 1 3 1 b a a On the other hand, for example, in the comparative example shown in, since the thermocoupleis arranged so as to be in contact with the nozzle, it is not possible to appropriately correct the temperature drop in the drying chamberD due to the accompanied flow AF, and uneven drying tends to occur in the coating filmformed on the surface of the base material.

As described above, according to the present embodiment, a coating film (coating layer) having good characteristics can be efficiently manufactured by adopting the suction roll, adopting the horizontal-type coating device, and improving the temperature control in the drying chamber.

Hereinafter, examples will be shown in order to describe the present embodiment more specifically, but the present invention is not limited to the following examples.

1 A coating layer was formed on the surface of a base material (porous film made of polyethylene) to form a separator (coated film) by using the apparatus for manufacturing the coated film according to the present embodiment. Namely, a coated film (separator) was formed while performing the tension cut of the base material by using suction rolls before and after the drying processing unit. Also, a horizontal-type coating device was used, and the temperature in the drying chamber was controlled by arranging the thermocouple in the regionA mentioned above.

A coating layer was formed on the surface of a base material to form a separator by using the apparatus for manufacturing the coated film according to the comparative example. Namely, a coated film (separator) was formed while performing the tension cut of the base material by using nip rolls before and after the drying processing unit. Also, a vertical-type coating device was used, and the temperature in the drying chamber was controlled by arranging the thermocouple on the nozzle.

With respect to the obtained samples (separators), wrinkles were visually determined, and the dry state was determined by touching with hand.

Table 1 below shows the processing conditions and determination results of each example and each comparative example.

TABLE 1 DRYING TEMPER- BASE COATING TENSION ATURE MATERIAL FILM LINE WINDING DRYING CONTROL- CONTROL- THICKNESS THICKNESS SPEED TENSION TEMPERATURE LING LING DRY [μm] [μm] [m/min] [N] [° C.] ROLL METHOD STATE WRINKLES COMPARATIVE 9 7 50 12 75 NIP POLL NOZZLE OK OK EXAMPLE 1 COMPARATIVE 7 7 50 12 75 NIP ROLL NOZZLE X X EXAMPLE 2 COMPARATIVE 9 7 50 12 80 NIP ROLL NOZZLE X X EXAMPLE 3 EXAMPLE 1 7 4 50 4 65 SUCTION TEMPER- OK OK ROLL ATURE IN OVEN EXAMPLE 2 5 4 30 4 50 SUCTION TEMPER- OK OK ROLL ATURE IN OVEN EXAMPLE 3 7 4 100 4 65 SUCTION TEMPER- OK OK ROLL ATURE IN OVEN

A coating layer having a film thickness of 7 μm was formed by using a base material having a film thickness of 9 μm. When the line speed was 50 m/min, the winding tension was 12 N. Also, the drying temperature was 75° C. In this case, there were no wrinkles (OK) and the dry state was good (OK).

10 FIG. 10 FIG.(A) 10 FIG.(B) A coating layer having a film thickness of 7 μm was formed by using a base material having a film thickness of 9 μm. When the line speed was 50 m/min, the winding tension was 12 N. Also, the drying temperature was 75° C. In this case, wrinkles occurred and the dry state was bad.is a diagram showing a sample of the comparative example 2. As shown in, winkles occur in the sample (separator). In, the wrinkles are clearly indicated by black lines.

A coating layer having a film thickness of 7 μm was formed by using a base material having a film thickness of 9 μm. When the line speed was 50 m/min, the winding tension was 12 N. Here, the drying temperature was 80° C. so as to improve the dry state, but on the contrary, wrinkles occurred and the dry state was deteriorated.

A coating layer having a film thickness of 4 μm was formed by using a base material having a film thickness of 7 μm. When the line speed was 50 m/min, the winding tension was 4 N. Also, the drying temperature was 65° C. In this case, there were no wrinkles (OK) and the dry state was good (OK).

A coating layer having a film thickness of 4 μm was formed by using a base material having a film thickness of 5 μm. When the line speed was 30 m/min, the winding tension was 4 N. Also, the drying temperature was 50° C. In this case, there were no wrinkles (OK) and the dry state was good (OK).

A coating layer having a film thickness of 4 μm was formed by using a base material having a film thickness of 7 μm. When the line speed was 100 m/min, the winding tension was 4 N. Also, the drying temperature was 65° C. In this case, there were no wrinkles (OK) and the dry state was good (OK).

The Gurley value deterioration rate was determined in the samples of the comparative example 1 and the example 3. The prepared sample was cut out and measured by using a Gurley-type automatic measuring machine. Here, the time that elapsed before the air of 100 cc passed through the sample (sheet) was measured as a Gurley value. In addition, the Gurley value for the base material before the formation of the coating layer was measured in the same manner and was defined as a reference Gurley value, and the Gurley value deterioration rate [((Gurley value−reference Gurley value)/reference Gurley value)×100%] was calculated.

The Gurley value deterioration rate of the sample of the comparative example 1 was 9.1%. On the other hand, the Gurley value deterioration rate of the sample of the example 3 was 8.5%. The Gurley value deterioration rate of the sample of the example 3 achieved the target of 10% or less, and was better than that of the comparative example 1.

9 FIG. In the comparative example 1, when the film thickness of the based material was as thick as 9 μm, a coated film (separator) with no wrinkles and a good dry state was obtained even in the apparatus of the comparative example. However, when the film thickness was as thin as 7 μm, wrinkles occurred and the dry state was bad in the apparatus of the comparative example. Further, in the comparative example 3, even when the film thickness of the base material was as thick as 9 μm, wrinkles occurred and the dry state was deteriorated on the contrary in the case of the drying method shown in.

On the other hand, in the example 1, although the film thickness of the base material was as thin as 7 μm, a coated film (separator) with no wrinkles and a good dry state was obtained.

In the example 2, even when the film thickness of the base material was further reduced to 5 μm, a coated film (separator) with no wrinkles and a good dry state was obtained.

In the example 3, even when the line speed was 100 m/min, a coated film (separator) having no wrinkles and a good dry state was obtained.

Further, in the examples 1 to 3, it was confirmed that the winding tension was as small as 4 N, and there was no problem even if the above-mentioned horizontal-type coating device was adopted. Also, it was confirmed that the line speed could be increased to 100 m/min or more because the winding tension was as small as 4 N.

Further, the temperature control of the drying oven functioned well, and the dry state was good in the examples 1 to 3 even though the drying temperatures (set temperatures) were lower than those of the comparative examples 1 to 3.

11 FIG. 31 31 1 31 31 b a b a. is a diagram showing the temperature changes in the drying chamber before and after improving the temperature control of the drying chamber. The vertical axis represents the temperature and the horizontal axis represents the time. The apparatus No. 1 (diamond mark) indicates the case after the improvement, that is, the case where the drying temperature was controlled by arranging the thermocouplebetween the side wall of the drying chamber on the upstream side and the nozzle(regionA), and the apparatus No. 0 (circular mark) indicates the case before the improvement, that is, the case where the drying temperature was controlled by arranging the thermocoupleso as to be in contact with the nozzle

31 1 a As shown in the figure, in the graph before the improvement, the temperature dropped sharply due to the influence of the accompanied flow, and since the temperature was controlled based on this drop, the excessive temperature rise occurred. On the other hand, when the nozzlewas arranged in the regionA mentioned above, the temperature drop due to the influence of the accompanied flow was slight, and the drying processing was performed at the set temperature of about 65° C.

By such temperature control, good drying could be performed without wrinkles even at the line speed of 100 m/min as shown in the example 3.

From the above-described examples and comparative examples, it was found that the coated film could be favorably formed by using the method and apparatus for manufacturing a coated film according to the present embodiment even when the film thickness of the base material was 9 μm or less, more preferably less than 9 μm, and still more preferably 7 μm or less. In particular, with respect to the separator, in order to improve the battery characteristics (particularly, the battery capacity), it has been desired to improve the strength and durability of the separator while reducing the thickness thereof. Therefore, it was found that it was effective to use the method and apparatus for manufacturing a coated film according to the present embodiment as the method and apparatus for manufacturing such a thin and high-strength separator.

From the above-described examples and comparative examples, it was found that the winding tension could be 12 N or less, more preferably less than 12 N, and still more preferably 4 N or less. As a result, it was found that the horizontal-type coating device could be adopted and a separator with good characteristics could be efficiently manufactured.

From the above-described examples and comparative examples, it was found that it was possible to achieve the processing speed (line speed) of the base material of 30 m/min or more, more preferably 50 m/min or more, and still more preferably 100 m/min or more, and a separator having good characteristics could be efficiently manufactured.

From the above-described examples and comparative examples, it was found that a favorable drying processing could be performed even when the drying temperature was relatively low, for example, less than 75° C., more preferably 65° C. or lower, and still more preferably 50° C. or lower. In particular, it was found that good drying processing could be performed because of the synergistic effect of the improvement of the temperature control and the adoption of the suction roll. Further, it was found that the influence of the accompanied flow could be reduced and favorable drying processing could be performed even when the processing was performed at a processing speed of 30 m/min or more, more preferably 50 m/min or more, and still more preferably 100 m/min or more.

In the present embodiment, an application example of the separator described in the first embodiment will be described. The separator can be applied to, for example, a lithium ion battery.

12 FIG. 12 FIG. 106 101 103 5 106 106 106 106 is a cross-sectional perspective view showing the configuration of a lithium ion battery. The lithium ion battery shown inhas a cylindrical can, and an electrode group in which strip-shaped positive electrode materialand negative electrode materialare wound with the separatorinterposed therebetween is housed in the can. A positive electrode current collecting tab on the upper end surface of the electrode group is joined to a positive electrode cap. A negative electrode current collecting tab on the lower end surface of the electrode group is joined to a bottom portion of the can. Note that an insulating coating (not shown) is provided on the outer peripheral surface of the can. Further, an electrolytic solution (not shown) is injected in the can. Although a cylindrical battery has been described here as an example, there is no limitation on the configuration of the battery, and for example, a square-type battery or a laminated-type battery can be used.

101 103 5 5 101 103 5 106 As described above, the lithium ion battery has the positive electrode material, the negative electrode material, the separator, and the electrolytic solution, and the separatoris arranged between the positive electrode materialand the negative electrode material. The separatorhas a large number of micropores. For example, when charging, that is, when a charger is connected between the positive electrode (positive electrode cap) and the negative electrode (bottom portion of the can), the lithium ions inserted in the positive electrode active material are desorbed and released into the electrolytic solution. The lithium ions released into the electrolytic solution move in the electrolytic solution, pass through the micropores of the separator, and reach the negative electrode. The lithium ions that have reached the negative electrode are inserted into the negative electrode active material that constitutes the negative electrode.

5 In this way, the lithium ions move back and forth between the positive electrode material and the negative electrode material through the micropores (not shown) provided in the separator, so that it is possible to perform charging and discharging repeatedly. By using the separator formed by using the method for manufacturing a coated film and the apparatus for manufacturing a coated film described in the first embodiment as this separator, the characteristics of the lithium ion battery can be improved. In addition, it is possible to form a lithium ion battery efficiently.

In the present embodiment, a method for manufacturing the base material (porous film) described in the first embodiment will be described. For example, the base material (porous film) described in the first embodiment can be manufactured by the following process.

13 FIG. 13 FIG. 1 is a schematic diagram showing the configuration of an apparatus (system) for manufacturing a porous film. For example, a plasticizer (liquid paraffin) and a polyolefin (for example, polyethylene) are put into a raw material supply unit of a twin screw kneading extruder (S) of, and the plasticizer and the polyolefin are kneaded in a kneading unit. The kneading conditions are, for example, 180° C. and 12 minutes, and the rotation speed of the shafts is 100 rpm.

2 3 2 The kneaded material (molten resin) is conveyed from a discharge unit to a T-die S, and the molten resin is cooled by a raw fabric cooling device Swhile being extruded from the slit of the T-die S, thereby forming a thin-film resin molding.

4 5 Next, the thin-film resin molding is stretched in the longitudinal direction by a first stretching device S, and is further stretched in the lateral direction by a second stretching device S.

6 6 Then, the stretched thin film is immersed in an organic solvent (for example, methylene chloride) in an extraction tank S. In the stretched thin film, the polyolefin (for example, polyethylene) and the plasticizer (paraffin) are in a phase-separated state. Specifically, the plasticizer (paraffin) forms nano-sized islands. This nano-sized plasticizer (paraffin) is removed (degreased) by the organic solvent (for example, methylene chloride) in the extraction tank S. In this way, a porous film can be formed.

7 7 8 Thereafter, by a third stretching device S, the thin film is dried and fixed by heat while being stretched in the lateral direction, and the internal stress during stretching is relaxed. Next, the porous film conveyed from the third stretching device Sis wound by a winding device S.

In this way, the porous film (base material of the first embodiment) can be manufactured.

8 3 1 FIG. b For example, the scroll-shaped porous film wound by the winding device Scan be set in the unwinding unit UW of the first embodiment (), and the coating layercan be formed on the surface thereof.

1 FIG. 1 FIG. 7 8 3 7 8 b Further, for example, the apparatus of the first embodiment () may be incorporated between the third stretching device Sand the winding device S. Namely, the coating layermay be formed by performing the corona processing on the surface of the porous film conveyed from the third stretching device S, applying the coating liquid, and then drying the liquid. In this case, the winding device Scorresponds to the winding unit WD of.

In this way, the separator may be formed by a continuous apparatus (system) from the formation of the porous film to the formation of the coating layer.

In the present embodiment, various application examples will be described.

14 FIG. 15 FIG. is a simplified schematic diagram showing the configuration of the apparatus for manufacturing the coated film according to the first embodiment, andis a simplified schematic diagram showing a configuration of an apparatus for manufacturing a coated film according to the present application example.

1 1 1 20 1 10 14 FIG. 15 FIG. In the first embodiment, the surface (first surface) of the base materialis subjected to the coating processing (see), but both surfaces of the base materialmay be subjected to the coating processing as shown in. In this case, since the coating film is also formed on the back surface of the base material, it is preferable to provide the suction roll SR on the upstream side from the coating processing unit (). Further, it is preferable to perform the corona processing on both surfaces of the base materialin the surface processing unit ().

20 1 FIG. 14 FIG. Note that the suction roll SR may be provided on the upstream side from the coating processing unit () (between 20 and UW) in the first embodiment (,).

16 FIG. 16 FIG. 20 30 1 30 1 1 30 2 30 1 30 2 30 1 30 2 30 1 30 2 is a simplified schematic diagram showing a configuration of an apparatus for manufacturing a coated film according to the present application example. In the application example 1, both surfaces are subjected to the coating processing in one coating processing unit () and both surfaces are simultaneously dried in one drying processing unit (). However, the coating processing and the drying processing may be sequentially performed for each of the both surfaces as shown in. Specifically, first, a coating film is provided on the front surface (first surface) of the base materialand dried by a drying processing unit (-), and then another coating film is provided on the back surface (second surface) of the base materialand dried by another drying processing unit (-). The surface processing may also be sequentially performed for each of the both surfaces. In this case, it is preferable to arrange the suction roll between the two drying processing units (-,-), before the drying processing unit (-), and after the drying processing unit (-). Note that the drying processing unit (-) and the drying processing unit (-) may be coupled.

1 FIG. 6 FIG. 17 FIG. In the first embodiment (,), the gravure coating device is used as a coating device, but another coating device may be used.is a perspective view showing a state of the coating using a slot die.

17 FIG.(A) 3 20 1 a a For example, in the slot die of, the coating filmis formed by applying the coating liquidfrom a manifold inside a die D onto the base materialthrough a slit (discharge unit) at the tip of the die.

17 FIG.(B) 1 2 20 1 20 2 1 3 1 3 2 a a a a Also, in the slot die of, a first die Dfor first coating liquid and a second die Dfor second coating liquid are provided, and the first coating liquidand the second coating liquidare sequentially applied onto the base material, so that a laminated film of a first coating filmand a second coating filmis formed.

17 FIG.(C) 1 1 2 1 3 1 1 3 2 1 1 a a Further, in the slot die of, the first die Dfor first coating liquid is arranged on the front surface side of the base materialand the second die Dfor second coating liquid is arranged on the back surface side of the base material, so that the first coating filmis formed on the front surface (first surface) of the base materialand the second coating filmis formed on the back surface (second surface) of the base material. Namely, both surfaces of the base materialcan be coated.

3 1 3 2 1 a a In addition, the laminated film of the first coating filmand the second coating filmmay be formed by preparing two gravure coating devices of the first embodiment. Further, the coating processing may be performed for both surfaces by arranging the gravure coating device of the first embodiment on both the front surface side and the back surface side of the base material.

1 FIG. In the first embodiment (), a suction roll is used as a roll for tension cut (roll for tension control), but another roll capable of tension cut by one-sided contact may be used.

1 1 As such a roll, in addition to the suction roll, an electrostatic adsorption roll or an air blowing roll can be used. In the electrostatic adsorption roll, the base materialis adsorbed by electrostatic adsorption, and in the air blowing roll, the base materialand the roll are brought into close contact with each other by blowing gas to the roll.

1 FIG. 8 FIG. In the first embodiment (,), a nozzle for discharging heated air is used for the drying processing, but the drying processing may be performed by a heater such as an infrared (IR) heater.

2 FIG. 17 FIG.(B) 20 1 a In the first embodiment (), one kind of coating liquidis applied on the base material, but another coating liquid may be further applied. Namely, the coating layer may have a multilayer structure (seeand the like). When forming the coating layer having a multilayer structure, the drying processing may be performed for each layer, or may be collectively performed at once.

1 FIG. 1 1 1 1 1 1 In the first embodiment (), a scroll-shaped (rolled strip-shaped) base materialis used, and the base materialunwound from the unwinding unit is conveyed to the processing unit. However, the shape of the base materialcan be changed as appropriate, and any shape can be adopted as long as it can be conveyed from the unloading unit (conveyor unit) to the processing unit. Further, even after the processing of the base material, it is not always necessary to wind the base material, and the base materialmay be conveyed to, for example, a battery assembling apparatus.

8 FIG. 1 2 3 1 1 In the first embodiment (), the improvement of the temperature control is described by taking the drying chamberD on the most upstream side as an example, but the same improvement may be applied also to the other drying chambersD andD. However, the drying chamberD on the most upstream side is greatly affected by the accompanied flow, and applying the improvement of temperature control to the drying chamberD is effective.

8 FIG. 1 Further, in the first embodiment (), the nozzle is provided at the center of the drying chamber, but the position of the nozzle is not limited and the nozzle may be arranged at another position. Also, a plurality of nozzles may be used, and in this case, a thermocouple (temperature sensor) is preferably arranged between the nozzle located on the most upstream side and the side wall of the drying chamber (cover) on the upstream side (regionA).

1 FIG. The position and number of rolls (guide rolls) R in the first embodiment () can be changed as appropriate.

In the foregoing, the invention made by the inventors of the present invention has been concretely described based on the embodiments and examples. However, it is needless to say that the present invention is not limited to the foregoing embodiments and examples and various modifications can be made within the range not departing from the gist thereof.

1 base material 1 a micropore 1 A region 1 D drying chamber 2 D drying chamber 3 a coating film 3 1 a first coating film 3 2 a second coating film 3 b coating layer 3 D drying chamber 5 separator 10 corona discharge irradiation device (surface processing unit) 20 gravure coating device (coating equipment, coating processing unit) 20 a coating liquid 20 b chamber (tank) 20 c blade 30 drying oven (drying processing unit) 30 1 -drying processing unit 30 2 -drying processing unit 31 a nozzle 31 b thermocouple 101 positive electrode material 103 negative electrode material 106 can AF accompanied flow BA region having a fan-shaped cross section CR coating roll D die 1 Dfirst die 2 Dsecond die DA heated dry air P hole R roll (guide roll) 1 Rnip roll (roll) 2 Rnip roll (roll) 1 Stwin-screw kneading extruder 2 Sdie 3 Sraw fabric cooling device 4 Sfirst stretching device 5 Ssecond stretching device 6 Sextraction tank 7 Sthird stretching device 8 Swinding device SR suction roll UW unwinding unit (winding device) WD winding unit (winding device)